Smithsonian miscellaneous collections

(1)

SMITHSONIAN MISCELLANEOUS COLLECTIONS VOLUME

111,

NUMBER

5

Eoebling Jf unb

1948-1949 REPORT ON THE

27.0074-DAY CYCLE IN WASHINGTON PRECIPITATION

BY

C. G.

ABBOT

Research Associate,SmithsonianInstitution

CITY OF WASHINGTON

PUBLISHED BY THE SMITHSONIAN INSTITUTION

MARCH

8,1949

(2)

ZU

^{^orb}Q0afttmore (prcee BALTIMORE,MI).,U.S.A.

(3)

ime

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2

SMITHSONIAN MISCELLANEOUS

COLLECTIONS VOL. Ill

numerals, in other words the "preferred days" for 1949.

These

preferred days should give, on the average, higher precipitation ])er day than all the other days of the year, but there is

no

high probability that precipitation will actually fall

on any

individual day

among

"preferred days," orwillnotfallon anyindividual other day.

Table^2.

—

Predicted dates when average daily precipitation should exceed averagedaily precipitationfor^allother datesin Washington,D. C,

for the year 1949

"Preferred" „ ,, « -.i t

cycle places Jan. Feb. Mar. Apr. May June

I 24 20 19 15 12 8

II 25 ²¹ 20 16 13 9

III 26 22 21 17 14 10

IV 27 23 22 18 IS II

V

1,28 24 23 19 16 12

XII 8 4 3 26 23 19

XIII 9 5 4,31 27 24 20

XV

II 7 6 2,29 26 22

XVII

13 9 ⁸ ⁴ ^1,28 ²⁴

XVIII 14 10 9 5 2,29 25

XXII 18 14 13 9 6 2,29

XXVI

22 18 17 13 10 6

XXVII

23 19 18 14 ^II 7

"Preferred" _

cycle places July Aug. Sept. Oct. Nov. Dec.

I 5 1.28 24 21 17 14

II 6 2,29 25 22 18 15

III 7 3,30 26 23 19 16

IV 8 4,31 27 24 20 17

V

9 5 1,28 25 21 18

XII 16 12 8 s 1,28 25

XIII 17 13 9 6 2,29 26

XV

19 15 II 8 4 1,28

XVII

21 17 13 10 6 3,30

XVIII 22 18 14 II 7 4,31

XXII

26 22 18 15 II 8

XXVI

3,30 26 22 19 15 12

XXVII

4,31 27 23 20 16 13

The

statistical tabulation of 27-day cycles, on which table 2 is based,began January i, 1924, andit indicated that the true cycleis

27.0074 days. In 25 years since

December

31, 1923, there

were

9.132 days. In339 ^cycles^of 27.0074 days thereare 9,155.50 days, or in round

numbers

23 days

more

than in the years 1924-1948.

Hence

thefirstday of the 340thcycle begins on January 24, 1949, asgivenin table2,correspondingto

Roman

numeralI.

Itshould beemphasizedthatthis predictionrelatesonlyto

Wash-

ington,D.

C-

2This paperwas finished on January 18, 1949, immediately after receiptof

\\'eatherBureaudatafor December1948.